Originally Posted by
Chris Scott
Not sure exactly what you mean by "calculate", but if not fully capable how could it offer Pitch-Alternate Law?
Hi Chris - what I'm saying is that your initial suggestion was that the "G"-loading system would possibly trim the aircraft nose-up at stick neutral as the speed appeared to decay. What I mean by "calculation" is that if the aircraft systems know that there is an double or triple erroneous airspeed indication, it drops to a mode whereby any protection or flight logic relying on airspeed is disabled. Surely this should be the case with the scenario you're describing - while "G" measurement itself is independent of the air data (thanks A33z), the logic you describe requires that data to work. So without airspeed data, how would the FCUs know to trim the aircraft nose up to maintain "G"?
Originally Posted by
vbp.net
To DozyWannabe #657. OK, AS is derived from 3 pitot tubes that could lead to problems if two of them are wrong but close enough to be taken as valid. Then why not compare AS history with GPS derived speed (history) together with thrust/attitude. I mean : compare the trends. If the plane is level flight, if thrust is not changed (even in turbulent weather) and a dire discrepency is noted (IAS significantly increasing/falling while GPS speed no change) wouldn't that be the case that AS should be highly suspected to be wrong ?
I don't mean the A/C should do something with that ! But the pilots might be warned.
Hi, and welcome.
The problem with what you're describing - as with any extra logic - is that you get into the engineering reliability maxim, which is that the more complex one makes a system, the probability of introducing errors also increases. The pilots are warned with the current system - an ECAM message "ADR DISAGREE". It's easy for such messages to get lost in the heat of the moment when things start to go pear-shaped however.
Originally Posted by
Smilin_Ed
Why didn't they notice it? It wasn't in their scan because they apparently were trained not to touch the pitch trim wheel(s) since pitch trim is always automatic and since it's automatic, why would you care?
Surely an attitude indicator displaying mostly blue would be a hell of a hint, however - and if you're trying to tell me that the ADI was not part of their scan, then that would highlight a terrifying oversight in their training (I suspect that isn't your position, however).
Also, at present we do not know AF's policy regarding training on the trim wheels. Svarin said that his current airline discourages their use, but he does not - as far as I know - fly for AF.
Originally Posted by
bubbers44
I think the inexperienced Colgan pilots resorted to a previous aircraft the captain had flown that had a tailplane stall recovery procedure that was opposite of wing stall recovery. This wasn't a problem in their aircraft and all pilots are taught to lower the nose in a stall, they raised it causing the crash.
That explains the Captain's reaction, but not that of the F/O, who I believe came straight to the Q400 and did not spend any time on the Saab. They both pulled back hard almost simultaneously. It's a well-known tendency for new pilots to instinctively pull back on the stick when receiving a stall warning (or indeed any unexpected shock) and is something that has to be trained out early on. As I recall the inference from the NTSB report on human factors suggested that fatigue and exhaustion may have caused this instinctive reaction to take over.
Something motivated them to pull back and all I can think of is an overspeed warning that was false.
I think if it was as simple as that then that information would have been released in the press note and the report would be coming along a lot sooner - along with a service bulletin or AD relating to the warning systems in the A330/340.
The fact they are holding all the pertinent information back that they have makes me think we will have some big surprises when they finally have to reveal it to the public.
I suspect that the BEA are in the process of a long drawn out human factors investigation to answer that question - these things take time. I don't think they're holding information back any more than any other investigative agency would at this stage, certainly not for any nefarious reasons - I think they honestly don't know (or didn't know at the time of the "note"'s release) why the PF reacted in the way he did. So in answer to your later question (paraphrased) of "why haven't they released the final report?" the answer is simply because it is not ready yet. I've already said several times that I doubt the NTSB or AAIB would be under so much pressure to release information early from some quarters on this board in the way the BEA currently is. Why is that, do you think?
Originally Posted by
RR_NDB
And the growing complexity concerns me.
Yet you're still advocating more technical solutions to implement in the design - surely if you were *that* concerned about complexity this would not be the case? The logic implemented in these aircraft (and those FBW airliners from other manufacturers) is actually pretty basic in modern computing terms. Asi I've said many times before it also uses obsolete technology (and always has) because the characteristics of obsolete hardware were already well-understood.
Originally Posted by
BOAC
Folks - why waste time on speculation? It is not rocket science to find out who was in the RHS. I guess that IF we need to know BEA will tell us. In any case, does it really matter?
With all due respect (and I do respect you - I remember you may well have "flogged [me] round in a Chippy" in my youth. For this and other reasons I will always think very carefully on the knowledge you share about aviation-related matters) - that's a bit rich.
We've had four threads and hundreds of pages, largely of speculation from people - some of them pilots - who nevertheless either do not/have not flown the Airbus FBW aircraft and/or do not understand the systems - including what they can/can't/will/won't do. These speculations have involved - among other things - wild theories about the computers going haywire due to a lightning strike, long-hidden software bugs coming out of hiding to neuter the unsuspecting pilots' authority and software designers and engineers wilfully ignoring pilots' input and building a confusing system out of hubris and a sense of superiority just for starters. Then we move on to the more subtle, but still noticeable digs at the technology - e.g. "confusers", "HAL", that old chestnut "Airbus one man/one dog flight deck" and an intent on the part of engineers to "reduce pilots to systems operators and monitors".
I realise that it is a privilege to talk with you all as a non-aviator myself, but if you can find me an aeronautical engineering forum where an undercurrent of disrespect towards pilots of that magnitude exists, then I believe you would consider it the height of rudeness and complain vociferously. Taking this attitude on the chin is IMO a small price to pay for what I get out of the time I spend on here, but I do ask that you think about what you're saying sometimes.
For the record, at present there is *no* evidence that the pilots were ever "confused" by what they were presented with. Alarmed, certainly - and with good reason - but not confused. There is also no evidence of any overspeed indication, no evidence of software-commanded flight controls outside of what was coming from the PF's sidestick and no evidence of any departure from their intended flight path which caused surprise. When the report arrives, we'll know better. It's also worth remembering that while we pore over the ACARS messages and the apparent crew actions, that the crew were not trying to diagnose the situation based on ECAM messages alone, but with a full set of available and functioning instruments with the brief exception of airspeed. I'm pretty sure that the "WRG" message, as I said before, was simply the FCUs playing catch-up with the already-triggered pitot data failure message, which would have led to the "ADR DISAGREE" message appearing on the flight deck. We're talking seconds and fractions of seconds here - in human terms, the computation delay was minimal.